A Chinese court on Monday jailed for life a former top aide to retired president Hu Jintao after finding him guilty of taking bribes, illegally obtaining state secrets and abuse of power during a secret trial in which his wife testified against him.

The verdict in the case, which the ruling Communist Party has said caused major damage to its image, brings to a close another chapter in President Xi Jinping's sweeping campaign against corruption which he began more than three years ago.

The party announced its investigation into the one-time aide to Hu, Ling Jihua, in December 2014. Ling had been demoted in September 2012 from a ministerial-level job, months after his son was killed in a crash involving a luxury sports car.

The court in the northern city of Tianjin, close to Beijing, held the case behind closed doors on June 7, according to a statement reported by the official Xinhua news agency.

"Ling Jihua took an extremely large amount of bribes. He obtained a large number of state secrets, and the crimes were very serious. He abused his power, and caused a terrible impact upon society," Xinhua said.

Ling took more than 77.08 million yuan ($11.6 million) in bribes personally and through his family, the court said, which listed several other high-profile former politicians also implicated in graft cases, including Bai Enpei, once the Communist Party boss in Yunnan province.

Bai went on trial last month but no verdict has been announced.

Ling accepted the facts of the case and did not contest them, Xinhua added.

"I accept all the charges and submit to the judgment," Xinhua quoted Ling as saying in his final statement. "Today's trial will be engraved in my memory."

Ling added that the trial was "solemn, meticulous, rational and civilised", embodying a combination of rule of law and humanitarian treatment, Xinhua added.

Ling's wife Gu Liping testified by video against him, with the help of multimedia presentations of evidence, Xinhua said. Deceased son, Ling Gu, was briefly mentioned as also having taken bribes, crimes the court said his father was aware of but did nothing about.

One source with ties to leadership told Reuters that investigators found a large amount of classified documents when they searched Ling's Beijing home.

The crimes Xinhua mentioned all occurred in 2012 and before that, when Ling had already stepped down as an aide to Hu in the party's general office, which oversees the sensitive day-to-day operations of the elite governing Politburo.

It was during this period that he got hold of state secrets from Huo Ke, who was still working in the general office, Xinhua said.

The report gave no details on the state secrets that Ling had obtained.

The trial was likely held in secret because of the state secret element, as happened with former state security chief Zhou Yongkang, jailed for life last year also for corruption.

It has never been possible to reach Ling for comment, and unclear who his lawyer was or if they were appointed for Ling by the party.

Ling's case had presented a dilemma for the government, because of his close connection with former president Hu, President Xi Jinping's predecessor.

A government spokesman denied last year that Hu was being implicated in the investigation and sources have told Reuters Hu approved of the case against Ling.